You might have heard that the transactions that miners include in their blocks are drawn from a mempool. But what exactly does this term mean? Find out below!
What Is A Mempool?
The term “mempool” derives from the combination of the words “memory” and “pool”. It refers to a database where a cryptocurrency node stores information on unconfirmed or pending transactions. Once a transaction is included in a block, it is removed from the mempool.
This term was first used by Bitcoin and later adopted by the Ethereum network. However, other blockchains use different words instead. For instance, on Geth, mempool is known as the “transaction pool”, whereas Parity uses the term “transaction queue”. However, essentially, all these expressions mean the same thing.
What You Need To Know About Mempools
As you can see from the mempool definition, it is somewhat like a waiting room for transactions that are yet to be confirmed. However, before a transaction is let into a mempool, it is continuously relaid from one node to another along the P2P network.
The nodes run a series of checks to verify the signatures, confirm that outputs do not exceed inputs, ensure that the funds have not already been spent, and so on. This process continues until the transaction has been widely propagated and is ready to be added to a block by miners.
Note that each node has its own mempool. This is due to the fact that anyone can run a node with their hardware of choice, and lower-end devices have a small amount of memory to store unconfirmed transactions, while the more advanced ones have a higher capacity for it. As a result, nodes have distinct configurations, sizes, and transaction counts.
Miners are mainly motivated by profits, so the transactions with higher fees are likely to be discarded from the mempool first. Since estimating the fees can be challenging, especially when block space is limited and demand is high, the data on the current unconfirmed transactions in a mempool can be effectively used as a reference point.
